QGIS API Documentation 3.29.0-Master (006c3c0232)
qgszonalstatistics.cpp
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1/***************************************************************************
2 qgszonalstatistics.cpp - description
3 ----------------------------
4 begin : August 29th, 2009
5 copyright : (C) 2009 by Marco Hugentobler
6 email : marco at hugis dot net
7 ***************************************************************************/
8
9/***************************************************************************
10 * *
11 * This program is free software; you can redistribute it and/or modify *
12 * it under the terms of the GNU General Public License as published by *
13 * the Free Software Foundation; either version 2 of the License, or *
14 * (at your option) any later version. *
15 * *
16 ***************************************************************************/
17
18#include "qgszonalstatistics.h"
19
20#include "qgsfeatureiterator.h"
21#include "qgsfeedback.h"
22#include "qgsgeometry.h"
24#include "qgsvectorlayer.h"
27#include "qgsrasterlayer.h"
28#include "qgslogger.h"
29#include "qgsproject.h"
30
31#include <QFile>
32
33QgsZonalStatistics::QgsZonalStatistics( QgsVectorLayer *polygonLayer, QgsRasterLayer *rasterLayer, const QString &attributePrefix, int rasterBand, QgsZonalStatistics::Statistics stats )
34 : QgsZonalStatistics( polygonLayer,
35 rasterLayer ? rasterLayer->dataProvider() : nullptr,
36 rasterLayer ? rasterLayer->crs() : QgsCoordinateReferenceSystem(),
37 rasterLayer ? rasterLayer->rasterUnitsPerPixelX() : 0,
38 rasterLayer ? rasterLayer->rasterUnitsPerPixelY() : 0,
39 attributePrefix,
40 rasterBand,
41 stats )
42{
43}
44
46 const QgsCoordinateReferenceSystem &rasterCrs, double rasterUnitsPerPixelX, double rasterUnitsPerPixelY, const QString &attributePrefix, int rasterBand, QgsZonalStatistics::Statistics stats )
47 : mRasterInterface( rasterInterface )
48 , mRasterCrs( rasterCrs )
49 , mCellSizeX( std::fabs( rasterUnitsPerPixelX ) )
50 , mCellSizeY( std::fabs( rasterUnitsPerPixelY ) )
51 , mRasterBand( rasterBand )
52 , mPolygonLayer( polygonLayer )
53 , mAttributePrefix( attributePrefix )
54 , mStatistics( stats )
55{
56}
57
59{
60 if ( !mRasterInterface )
61 {
62 return RasterInvalid;
63 }
64
65 if ( mRasterInterface->bandCount() < mRasterBand )
66 {
67 return RasterBandInvalid;
68 }
69
70 if ( !mPolygonLayer || mPolygonLayer->geometryType() != QgsWkbTypes::PolygonGeometry )
71 {
72 return LayerTypeWrong;
73 }
74
75 QgsVectorDataProvider *vectorProvider = mPolygonLayer->dataProvider();
76 if ( !vectorProvider )
77 {
78 return LayerInvalid;
79 }
80
81 QMap<QgsZonalStatistics::Statistic, int> statFieldIndexes;
82
83 //add the new fields to the provider
84 int oldFieldCount = vectorProvider->fields().count();
85 QList<QgsField> newFieldList;
87 {
100 } )
101 {
102 if ( mStatistics & stat )
103 {
104 QString fieldName = getUniqueFieldName( mAttributePrefix + QgsZonalStatistics::shortName( stat ), newFieldList );
105 QgsField field( fieldName, QVariant::Double, QStringLiteral( "double precision" ) );
106 newFieldList.push_back( field );
107 statFieldIndexes.insert( stat, oldFieldCount + newFieldList.count() - 1 );
108 }
109 }
110
111 vectorProvider->addAttributes( newFieldList );
112
113 long featureCount = vectorProvider->featureCount();
114
115 QgsFeatureRequest request;
116 request.setNoAttributes();
117
118 request.setDestinationCrs( mRasterCrs, QgsProject::instance()->transformContext() );
119 QgsFeatureIterator fi = vectorProvider->getFeatures( request );
120 QgsFeature feature;
121
122 int featureCounter = 0;
123
124 QgsChangedAttributesMap changeMap;
125 while ( fi.nextFeature( feature ) )
126 {
127 ++featureCounter;
128 if ( feedback && feedback->isCanceled() )
129 {
130 break;
131 }
132
133 if ( feedback )
134 {
135 feedback->setProgress( 100.0 * static_cast< double >( featureCounter ) / featureCount );
136 }
137
138 QgsGeometry featureGeometry = feature.geometry();
139
140 QMap<QgsZonalStatistics::Statistic, QVariant> results = calculateStatistics( mRasterInterface, featureGeometry, mCellSizeX, mCellSizeY, mRasterBand, mStatistics );
141
142 if ( results.empty() )
143 continue;
144
145 QgsAttributeMap changeAttributeMap;
146 for ( const auto &result : results.toStdMap() )
147 {
148 changeAttributeMap.insert( statFieldIndexes.value( result.first ), result.second );
149 }
150
151 changeMap.insert( feature.id(), changeAttributeMap );
152 }
153
154 vectorProvider->changeAttributeValues( changeMap );
155 mPolygonLayer->updateFields();
156
157 if ( feedback )
158 {
159 if ( feedback->isCanceled() )
160 return Canceled;
161
162 feedback->setProgress( 100 );
163 }
164
165 return Success;
166}
167
168QString QgsZonalStatistics::getUniqueFieldName( const QString &fieldName, const QList<QgsField> &newFields )
169{
170 QgsVectorDataProvider *dp = mPolygonLayer->dataProvider();
171
172 if ( !dp->storageType().contains( QLatin1String( "ESRI Shapefile" ) ) )
173 {
174 return fieldName;
175 }
176
177 QList<QgsField> allFields = dp->fields().toList();
178 allFields.append( newFields );
179 QString shortName = fieldName.mid( 0, 10 );
180
181 bool found = false;
182 for ( const QgsField &field : std::as_const( allFields ) )
183 {
184 if ( shortName == field.name() )
185 {
186 found = true;
187 break;
188 }
189 }
190
191 if ( !found )
192 {
193 return shortName;
194 }
195
196 int n = 1;
197 shortName = QStringLiteral( "%1_%2" ).arg( fieldName.mid( 0, 8 ) ).arg( n );
198 found = true;
199 while ( found )
200 {
201 found = false;
202 for ( const QgsField &field : std::as_const( allFields ) )
203 {
204 if ( shortName == field.name() )
205 {
206 n += 1;
207 if ( n < 9 )
208 {
209 shortName = QStringLiteral( "%1_%2" ).arg( fieldName.mid( 0, 8 ) ).arg( n );
210 }
211 else
212 {
213 shortName = QStringLiteral( "%1_%2" ).arg( fieldName.mid( 0, 7 ) ).arg( n );
214 }
215 found = true;
216 }
217 }
218 }
219 return shortName;
220}
221
223{
224 switch ( statistic )
225 {
226 case Count:
227 return QObject::tr( "Count" );
228 case Sum:
229 return QObject::tr( "Sum" );
230 case Mean:
231 return QObject::tr( "Mean" );
232 case Median:
233 return QObject::tr( "Median" );
234 case StDev:
235 return QObject::tr( "St dev" );
236 case Min:
237 return QObject::tr( "Minimum" );
238 case Max:
239 return QObject::tr( "Maximum" );
240 case Range:
241 return QObject::tr( "Range" );
242 case Minority:
243 return QObject::tr( "Minority" );
244 case Majority:
245 return QObject::tr( "Majority" );
246 case Variety:
247 return QObject::tr( "Variety" );
248 case Variance:
249 return QObject::tr( "Variance" );
250 case All:
251 return QString();
252 }
253 return QString();
254}
255
257{
258 switch ( statistic )
259 {
260 case Count:
261 return QStringLiteral( "count" );
262 case Sum:
263 return QStringLiteral( "sum" );
264 case Mean:
265 return QStringLiteral( "mean" );
266 case Median:
267 return QStringLiteral( "median" );
268 case StDev:
269 return QStringLiteral( "stdev" );
270 case Min:
271 return QStringLiteral( "min" );
272 case Max:
273 return QStringLiteral( "max" );
274 case Range:
275 return QStringLiteral( "range" );
276 case Minority:
277 return QStringLiteral( "minority" );
278 case Majority:
279 return QStringLiteral( "majority" );
280 case Variety:
281 return QStringLiteral( "variety" );
282 case Variance:
283 return QStringLiteral( "variance" );
284 case All:
285 return QString();
286 }
287 return QString();
288}
289
291QMap<int, QVariant> QgsZonalStatistics::calculateStatisticsInt( QgsRasterInterface *rasterInterface, const QgsGeometry &geometry, double cellSizeX, double cellSizeY, int rasterBand, QgsZonalStatistics::Statistics statistics )
292{
293 const auto result { QgsZonalStatistics::calculateStatistics( rasterInterface, geometry, cellSizeX, cellSizeY, rasterBand, statistics ) };
294 QMap<int, QVariant> pyResult;
295 for ( auto it = result.constBegin(); it != result.constEnd(); ++it )
296 {
297 pyResult.insert( it.key(), it.value() );
298 }
299 return pyResult;
300}
302
303QMap<QgsZonalStatistics::Statistic, QVariant> QgsZonalStatistics::calculateStatistics( QgsRasterInterface *rasterInterface, const QgsGeometry &geometry, double cellSizeX, double cellSizeY, int rasterBand, QgsZonalStatistics::Statistics statistics )
304{
305 QMap<QgsZonalStatistics::Statistic, QVariant> results;
306
307 if ( geometry.isEmpty() )
308 return results;
309
310 QgsRectangle rasterBBox = rasterInterface->extent();
311
312 QgsRectangle featureRect = geometry.boundingBox().intersect( rasterBBox );
313
314 if ( featureRect.isEmpty() )
315 return results;
316
317 bool statsStoreValues = ( statistics & QgsZonalStatistics::Median ) ||
318 ( statistics & QgsZonalStatistics::StDev ) ||
319 ( statistics & QgsZonalStatistics::Variance );
320 bool statsStoreValueCount = ( statistics & QgsZonalStatistics::Minority ) ||
321 ( statistics & QgsZonalStatistics::Majority );
322
323 FeatureStats featureStats( statsStoreValues, statsStoreValueCount );
324
325 int nCellsXProvider = rasterInterface->xSize();
326 int nCellsYProvider = rasterInterface->ySize();
327
328 int nCellsX, nCellsY;
329 QgsRectangle rasterBlockExtent;
330 QgsRasterAnalysisUtils::cellInfoForBBox( rasterBBox, featureRect, cellSizeX, cellSizeY, nCellsX, nCellsY, nCellsXProvider, nCellsYProvider, rasterBlockExtent );
331
332 featureStats.reset();
333 QgsRasterAnalysisUtils::statisticsFromMiddlePointTest( rasterInterface, rasterBand, geometry, nCellsX, nCellsY, cellSizeX, cellSizeY, rasterBlockExtent, [ &featureStats ]( double value ) { featureStats.addValue( value ); } );
334
335 if ( featureStats.count <= 1 )
336 {
337 //the cell resolution is probably larger than the polygon area. We switch to precise pixel - polygon intersection in this case
338 featureStats.reset();
339 QgsRasterAnalysisUtils::statisticsFromPreciseIntersection( rasterInterface, rasterBand, geometry, nCellsX, nCellsY, cellSizeX, cellSizeY, rasterBlockExtent, [ &featureStats ]( double value, double weight ) { featureStats.addValue( value, weight ); } );
340 }
341
342 // calculate the statistics
343
344 if ( statistics & QgsZonalStatistics::Count )
345 results.insert( QgsZonalStatistics::Count, QVariant( featureStats.count ) );
346 if ( statistics & QgsZonalStatistics::Sum )
347 results.insert( QgsZonalStatistics::Sum, QVariant( featureStats.sum ) );
348 if ( featureStats.count > 0 )
349 {
350 double mean = featureStats.sum / featureStats.count;
351 if ( statistics & QgsZonalStatistics::Mean )
352 results.insert( QgsZonalStatistics::Mean, QVariant( mean ) );
353 if ( statistics & QgsZonalStatistics::Median )
354 {
355 std::sort( featureStats.values.begin(), featureStats.values.end() );
356 int size = featureStats.values.count();
357 bool even = ( size % 2 ) < 1;
358 double medianValue;
359 if ( even )
360 {
361 medianValue = ( featureStats.values.at( size / 2 - 1 ) + featureStats.values.at( size / 2 ) ) / 2;
362 }
363 else //odd
364 {
365 medianValue = featureStats.values.at( ( size + 1 ) / 2 - 1 );
366 }
367 results.insert( QgsZonalStatistics::Median, QVariant( medianValue ) );
368 }
369 if ( statistics & QgsZonalStatistics::StDev || statistics & QgsZonalStatistics::Variance )
370 {
371 double sumSquared = 0;
372 for ( int i = 0; i < featureStats.values.count(); ++i )
373 {
374 double diff = featureStats.values.at( i ) - mean;
375 sumSquared += diff * diff;
376 }
377 double variance = sumSquared / featureStats.values.count();
378 if ( statistics & QgsZonalStatistics::StDev )
379 {
380 double stdev = std::pow( variance, 0.5 );
381 results.insert( QgsZonalStatistics::StDev, QVariant( stdev ) );
382 }
383 if ( statistics & QgsZonalStatistics::Variance )
384 results.insert( QgsZonalStatistics::Variance, QVariant( variance ) );
385 }
386 if ( statistics & QgsZonalStatistics::Min )
387 results.insert( QgsZonalStatistics::Min, QVariant( featureStats.min ) );
388 if ( statistics & QgsZonalStatistics::Max )
389 results.insert( QgsZonalStatistics::Max, QVariant( featureStats.max ) );
390 if ( statistics & QgsZonalStatistics::Range )
391 results.insert( QgsZonalStatistics::Range, QVariant( featureStats.max - featureStats.min ) );
392 if ( statistics & QgsZonalStatistics::Minority || statistics & QgsZonalStatistics::Majority )
393 {
394 QList<int> vals = featureStats.valueCount.values();
395 std::sort( vals.begin(), vals.end() );
396 if ( statistics & QgsZonalStatistics::Minority )
397 {
398 double minorityKey = featureStats.valueCount.key( vals.first() );
399 results.insert( QgsZonalStatistics::Minority, QVariant( minorityKey ) );
400 }
401 if ( statistics & QgsZonalStatistics::Majority )
402 {
403 double majKey = featureStats.valueCount.key( vals.last() );
404 results.insert( QgsZonalStatistics::Majority, QVariant( majKey ) );
405 }
406 }
407 if ( statistics & QgsZonalStatistics::Variety )
408 results.insert( QgsZonalStatistics::Variety, QVariant( featureStats.valueCount.count() ) );
409 }
410
411 return results;
412}
This class represents a coordinate reference system (CRS).
Wrapper for iterator of features from vector data provider or vector layer.
bool nextFeature(QgsFeature &f)
This class wraps a request for features to a vector layer (or directly its vector data provider).
QgsFeatureRequest & setDestinationCrs(const QgsCoordinateReferenceSystem &crs, const QgsCoordinateTransformContext &context)
Sets the destination crs for feature's geometries.
QgsFeatureRequest & setNoAttributes()
Set that no attributes will be fetched.
The feature class encapsulates a single feature including its unique ID, geometry and a list of field...
Definition: qgsfeature.h:56
QgsGeometry geometry
Definition: qgsfeature.h:67
Q_GADGET QgsFeatureId id
Definition: qgsfeature.h:64
Base class for feedback objects to be used for cancellation of something running in a worker thread.
Definition: qgsfeedback.h:45
bool isCanceled() const SIP_HOLDGIL
Tells whether the operation has been canceled already.
Definition: qgsfeedback.h:54
void setProgress(double progress)
Sets the current progress for the feedback object.
Definition: qgsfeedback.h:63
Encapsulate a field in an attribute table or data source.
Definition: qgsfield.h:51
QString name
Definition: qgsfield.h:60
QList< QgsField > toList() const
Utility function to return a list of QgsField instances.
Definition: qgsfields.cpp:212
int count() const
Returns number of items.
Definition: qgsfields.cpp:133
A geometry is the spatial representation of a feature.
Definition: qgsgeometry.h:164
bool isEmpty() const
Returns true if the geometry is empty (eg a linestring with no vertices, or a collection with no geom...
QgsRectangle boundingBox() const
Returns the bounding box of the geometry.
static QgsProject * instance()
Returns the QgsProject singleton instance.
Definition: qgsproject.cpp:476
Base class for processing filters like renderers, reprojector, resampler etc.
virtual int xSize() const
Gets raster size.
virtual int bandCount() const =0
Gets number of bands.
virtual int ySize() const
virtual QgsRectangle extent() const
Gets the extent of the interface.
Represents a raster layer.
A rectangle specified with double values.
Definition: qgsrectangle.h:42
bool isEmpty() const
Returns true if the rectangle is empty.
Definition: qgsrectangle.h:469
QgsRectangle intersect(const QgsRectangle &rect) const
Returns the intersection with the given rectangle.
Definition: qgsrectangle.h:333
This is the base class for vector data providers.
long long featureCount() const override=0
Number of features in the layer.
virtual QString storageType() const
Returns the permanent storage type for this layer as a friendly name.
virtual bool changeAttributeValues(const QgsChangedAttributesMap &attr_map)
Changes attribute values of existing features.
QgsFields fields() const override=0
Returns the fields associated with this data provider.
QgsFeatureIterator getFeatures(const QgsFeatureRequest &request=QgsFeatureRequest()) const override=0
Query the provider for features specified in request.
virtual bool addAttributes(const QList< QgsField > &attributes)
Adds new attributes to the provider.
Represents a vector layer which manages a vector based data sets.
Q_INVOKABLE QgsWkbTypes::GeometryType geometryType() const
Returns point, line or polygon.
void updateFields()
Will regenerate the fields property of this layer by obtaining all fields from the dataProvider,...
QgsVectorDataProvider * dataProvider() FINAL
Returns the layer's data provider, it may be nullptr.
A class that calculates raster statistics (count, sum, mean) for a polygon or multipolygon layer and ...
static QString shortName(QgsZonalStatistics::Statistic statistic)
Returns a short, friendly display name for a statistic, suitable for use in a field name.
Statistic
Enumeration of flags that specify statistics to be calculated.
@ Minority
Minority of pixel values.
@ Variety
Variety (count of distinct) pixel values.
@ Variance
Variance of pixel values.
@ Mean
Mean of pixel values.
@ Majority
Majority of pixel values.
@ Range
Range of pixel values (max - min)
@ Min
Min of pixel values.
@ Sum
Sum of pixel values.
@ StDev
Standard deviation of pixel values.
@ Max
Max of pixel values.
@ Median
Median of pixel values.
Result
Error codes for calculation.
@ RasterInvalid
Raster layer is invalid.
@ RasterBandInvalid
The raster band does not exist on the raster layer.
@ LayerTypeWrong
Layer is not a polygon layer.
@ Canceled
Algorithm was canceled.
@ LayerInvalid
Layer is invalid.
QgsZonalStatistics::Result calculateStatistics(QgsFeedback *feedback)
Runs the calculation.
static QString displayName(QgsZonalStatistics::Statistic statistic)
Returns the friendly display name for a statistic.
QgsZonalStatistics(QgsVectorLayer *polygonLayer, QgsRasterLayer *rasterLayer, const QString &attributePrefix=QString(), int rasterBand=1, QgsZonalStatistics::Statistics stats=QgsZonalStatistics::Statistics(QgsZonalStatistics::Count|QgsZonalStatistics::Sum|QgsZonalStatistics::Mean))
Convenience constructor for QgsZonalStatistics, using an input raster layer.
QMap< int, QVariant > QgsAttributeMap
Definition: qgsattributes.h:42
QMap< QgsFeatureId, QgsAttributeMap > QgsChangedAttributesMap
Definition: qgsfeature.h:908
const QgsField & field
Definition: qgsfield.h:463
const QgsCoordinateReferenceSystem & crs